This invention relates to chemical-mechanical polishing (CMP) and more particularly to a dedicated polishing pad conditioning machine.
Chemical-mechanical polishing is a process used by semiconductor manufacturers to planarize the surface of an integrated circuit so that the chip can have multiple, flat layers. During the CMP process, a machine is used to press a wafer and a polishing pad into contact at a selected pressure. Both the pad and the wafer are turned at a given rotational velocity and a slurry containing a liquid and abrasive particles is pumped into the interface of the pad and the wafer to increase the material removal rate. In order for the CMP process to be effective, defects on the wafer surface must be kept to a minimum. Recently, scratching of the wafer surface has emerged as the dominant defect during CMP.
The semiconductor manufacturing industry has used a “quick fix” approach to the scratching problem. Currently, the industry uses the chemical-mechanical polishing tool itself to condition a new pad by using the CMP machine to polish approximately 50 Cu-coated wafers that are then discarded later. This procedure is very inefficient because the CMP polishing tool was designed with the sole purpose of polishing wafers, not conditioning polishing pads. Currently, the conditioning process using the CMP polishing machine takes approximately four hours and must be repeated every 24 hours, per polishing machine. Therefore, valuable machine time and costly consumables (i.e., wafers and environmentally-harmful slurry) are wasted.
It is therefore an object of the present invention to provide a machine and process that will enable a new polishing pad to be conditioned apart from the use of the CMP polishing machine. Thus, the CMP polishing machines will not have to experience four hours of downtime every day. Another object of the invention is to accelerate the pad conditioning process by making it more efficient by taking only one-tenth of the previous amount of time and which uses no wafers.